Add new regression and ensemble experiment configurations for V2-M and OrthoBridge

- Introduced multiple regression experiment configurations targeting vf_md, including:
  - cd_solo_reg_set.json: CD tower only regression setup.
  - img_solo_reg_set.json: Image tower only regression setup.
  - reg_head_epoch_sweep.json: Baseline regression sweeps at different epochs (50, 75, 100).
  - reg_head_set.json: Various regression setups including baseline and OrthoBridge configurations.
  - single_eye_reg.json: Single-eye regression setup for worst-eye aggregation analysis.

- Added ensemble configurations for OrthoBridge with different inner bridges:
  - ortho_alts_ensemble.json: Ensemble tests with ConcatBridge, PairwiseAdditiveBridge, and GatedAdditiveBridge.
  - ortho_alts_tritower.json: Tritower tests with the same inner bridges.

- Created V2-M specific configurations:
  - baseline_reg_nt50.json: Regression baseline with V2-M backbone.
  - geom_vec_gt.json and geom_vec_unet.json: Geometry vector injection experiments with V2-M.
  - single_l1_bridges.json: Single-eye ensemble experiments with various bridge types.
  - tritower_geom_gt.json: Tritower setup with GT contour-rasterized masks.

- Promoted existing experiments to higher repetitions for robustness.

v4/scripts/experiments/phase6_v4/geom_vec_unet_10rep.json

@@ -0,0 +1,7 @@
+[
+  {
+    "_note": "Geometry-vector injection from UNet-derived segmentation, bumped to 10 reps to round out the refugelike geometry panel alongside ensemble_fused/no_geom (0.8979, n=10), ensemble_fused/geom_gt (0.9121, n=10), tri_v1/baseline_tri (0.8932, n=10), and tri_v1/baseline_solo (0.6833, n=10). Use the existing ensemble_fused_geom_unet.json base config which already wires up the EPC geometry_vectors channel.",
+    "run_name": "experiments/phase6_v4/ensemble_geom_vec_unet",
+    "reps": 10
+  }
+]